AWWA JAW59058

The removal of natural organic matter (NOM) is a primary concern for the drinking water industry, but little attention has been paid to the practice of enhanced softening, its benefits, and associated challenges. Additionally, no previous reports had included the effects of softening on the formation of disinfection byproducts. This article provides utilities that use softening with a blueprint for studying how their own operations might be altered to achieve better NOM removals and reduced disinfection byproduct formation Utilities that use softening will be interested in the study results describing removal of NOM in softening, as well as the effects of silica on softening and NOM removal and the effects of bromide on the speciation of trihalomethanes. The authors also discuss how enhanced softening may be able to achieve the US Environmental Protection Agency's requirements for removal of NOM without complete precipitation of magnesium hydroxide [Mg(OH)₂]. Although Mg(OH)₂ is a more efficient adsorbent of NOM, calcium carbonate, which precipitates at lower pH and therefore requires lower lime dosage in softening, is also capable of substantial NOM removal. Includes 20 references, tables, figures.